Improvement of the Behavior of Cement Mortar by Vinegar Treatment of the Flax Fibers Reinforcement

International audienceThe association between plant fibers and a cement matrix generates different problems, in the fresh state and in the hardened state of the material. Several studies propose to treat the plant fibers with chemical, physical or thermal treatments. The aim of this work is to ameliorate the behavior of a cement mortar incorporating short flax fibers by treating them with white vinegar which is a non-polluting product. This natural treatment was chosen in order to clean the fiber's surface by partial removal of the non-cellulosic compounds known to deeply disturb the behavior of the material in the fresh state especially in terms of consistency and setting time. Two treatment's immersion time were tested, 2 and 24 hours. To evaluate the efficiency of this treatment, tensile, thermal and water absorption tests were conducted on treated and raw fibers. Different mortar formulations (Control mortar, Mortar with raw fibers and mortar with treated fibers) were prepared and characterised in the fresh and hardened states. Results show a significant reduction of the water absorption of the fibers and an increase of their average tensile strength. The properties of the cement composites have also been improved in terms of consistency, initial setting time and mechanical performances